The marked increase in battery usage has created a need for an improved battery control system. The majority of prior art charging systems incorporate voltage level of the battery as a reference to determine the level of charge, and this method has many drawbacks. Firstly, a small change in voltage of -1% with a corresponding 0.4 volt change with a 36 volt system represents a 10% change in estimated battery capacity. Secondly, this small change is also affected by the load in amperes on the battery. Thirdly, temperature of the electrolyte and the specific gravity of the electrolyte cause further inaccuracies when voltage is used as a reference.
The battery control system disclosed herein monitors battery capacity using a novel idea of means employing the latest technologies, incorporating a microcomputer to convert load current of the battery into ampere hours. The ampere hours are then converted into percentage of battery capacity and displayed as "Battery Capacity Remaining", analogous to a fuel level gauge. Software programming in the microcomputer is used to control functions that are incorporated in this battery control system. The system determines the appropriate charger turn-off point, it indicates a bad battery or cell, it gives a warning of extreme discharge conditions, it shows lack of charging power when the charger is plugged in, it automatically handles power interrupts, and it governs long term storage of batteries without overcharge. An external or built-in electronic or electromechanical counter is connected to the battery control system to indicate the ampere hours total consumed by the equipment, and during discharge this indicator or counter accumulates ampere hours and then outputs that value to the display. The amount of overcharge appropriate for the particular battery is readily selected for accurate turn-off of the charger, thereby extending battery life and minimizing water boil-off during charge.
It is a general object of this invention to convert load current of the battery into ampere hours seen as a percentage of the battery capacity and displayed as a remaining quantity of energy. It is also an object of this invention to provide control of battery charging by means of software programming in a microcomputer, to determine charge turn-off and charge turn-on points, to indicate a bad battery or cell thereof, to warn of extreme discharge conditions, to show lack of power to the charger, to automatically handle power interruptions, to permit long term storage without overcharge, to count and display ampere hours consumed, and to selectively determine the amount of overcharge for a particular battery or set of batteries.
The foregoing and various other objects and features of this invention will be apparent and fully understood from the following detailed description of the typical preferred form and applications thereof, throughout which description reference is made to the accompanying drawings.